This invention relates to a light-sensitive litho printing plate requiring no dampening water, more specifically to a light-sensitive litho printing plate requiring no dampening water improved in abrasion resistance of an ink repellant layer and bending resistance of a plate, and also excellent in press life.
In the prior art, as a light-sensitive litho printing plate (hereinafter called "plate material" if necessary) requiring no dampening water, one having a light-sensitive layer and an ink repellant layer provided successively by coating on a support has been known. By subjecting this plate material to exposure and development, a litho printing plate (hereinafter called "printing plate" if necessary) requiring no dampening water can be obtained.
Generally speaking, in such a plate material, for improving adhesion property between a support and a light-sensitive layer, a primer layer is provided therebetween.
For example, in Japanese Unexamined Patent Publication No. 7049/1990, there is disclosed a light-sensitive litho printing plate requiring no dampening water having a primer layer, a light-sensitive layer and an ink repellant layer on a support. However, when this plate material is processed by using an automatic processor, an ink repellant layer is rubbed by a development brush, whereby flaws are liable to be generated on this ink repellant layer, and when the printing plate was set in a printing machine, the plate is bended, whereby cracks at the bending portion and peel-off of the ink repellant layer are generated to bring about a problem that press life is lowered.
As described above, in the case of a plate material having a primer layer, flaws are liable to be generated on an ink repellant layer, and cracks at a bending portion and peel-off of an ink repellant layer are liable to be generated. When a primer layer is made elastic in order to prevent these problems, stress applied to an ink repellant layer is alleviated by a primer layer to endure this stress, whereby flaws are hardly generated.
Also at the time of bending a plate, stress from a support is alleviated similarly by a primer layer, whereby generation of cracks at the bending portion can be prevented.